Welcome to my Sysmax/Nitecore Intellicharger i4 V2 review.
UPDATE JANUARY 6, 2012: I have now reviewed a similar version of this charger, under the Jetbeam-specific branding - the Jetbeam i4 PRO.
The initial iteration of the i4 charger sparked a lot of interest here, due to its stated ability to "intelligently" handle both Li-ions and standard NiMH/NiCd rechargeable batteries.
There were some problems with the first version of this charger (especially when run on North American 110V AC power), resulting in a model recall. This review will look at the new and revised V2, which addresses the earlier issues and adds some new features.
This review will be done in the style of my earlier Xtar WP2-II review. I am not as well versed in electronics or circuitry as some of the other members here, so I suggest you consult with the experts if you want to know more than just the basic current/voltage runtime relationships presented here.
Please see my original charger round-up review for more background on my testing method, and comparison to a number of basic chargers.
If you are looking for more information on how to perform measurement/testing on chargers, please see HKJ's excellent Measurement on flashlight page.
i4 Intellicharger V2 Reported Specifications
- Li-ion: 26650, 22650, 18650, 17670, 18490, 17500, 17335, 16340 (RCR), 14500, 10440
- NiMH / NiCd: AA, AAA, C
- Input Voltage: AC 100-240V 50/60Hz or DC 12V
- Input power: 10W
- Output Voltage: 4.2V +/- 1% / 1.48V +/- 1%
- Output Current: 350mA x 4 / 750 mA x 2
- Capable of charging 4 batteries simultaneously
- Each of the four battery slots monitors and charges independently
- Automatically identifies Li-ion, Ni-MH and Ni-Cd rechargeable batteries
- Features three charging modes (CC, CV and Trickle Charge)
- Automatically detects battery status and selects the appropriate voltage and charge mode
- 3 Color LED displays charging progress for each battery
- Automatically stops charging when complete
- Features reverse polarity protection
- Designed for optimal heat dissipation
- Certified by both RoHS and CE
- Dimensions: 139mm x 96mm x36mm
- Weight: 156g (without batteries)
What's New in Version 2
- The charging slot is now 2cm longer than the v1 version, to accommodate larger protected cells. (Reviewer's Note: I believe they meant to say 2mm longer)
- The charging current drops to 750mA when charging two batteries at position #1 & #3. The current is still 750mA for and will alternate charge cycle once every second for each battery. When charging two batteries installed in slot #1 & #2 they will get 750mh respectively. The result is: charging at slot #1 & #2 will be faster than charging at slot #1 & #3 (Reviewer's Note: #2 & #4 are similarly paired, like #1 & #3)
- Improved charging capability/safety when charging 10440 li-ion batteries
- Works properly with US 110V System
- MSRP: ~$25
Note the above is what the manufacturer reports for the charger – scroll down to see my actual review findings.
My i4 V2 came with just a standard 110 AC power adapter. The unit supports 100 – 240V AC, 50/60Hz, so those outside of North America can use it fine (with the appropriate terminal plug). A 12V DC car adapter is available separately.
The cabling and overall build seem good (good length on the cables, solid base unit). The battery trays are spring-mounted, and can easily accommodate any size from RCR to 18650 without spacers. However, I found the springs lacked lube on my sample, and a couple of them were very stiff to operate out of the box. You will likely need to add some lube yourself, which is an inconvenience for the general consumer.
As explained in the manual, while the charger has four bays, it actually only has two independent channels. If you want to charge two cells independently of each other (i.e., each charged at the full 750mA current the unit is capable of), you need to place the cells in bays #1 & #2, #2 & #3, #1 & #4, or #3 & #4.
If you place the cells in the paired bays #1 & #3, or #2 & #4, the charging current will be split between the cells. Rather than just cutting in half (i.e., 375mA per bay), the current remains at 750mA for each bay – but it alternates charging by cycling off/on once every second for each battery. This effectively results in the same thing, but the cell is actually being charged at 750mA for a 1sec on, 1sec off, cycle.
This is explained in the manual, but it would be good have the charger unit bays labelled somehow. Scroll down to see my actual testing results.
Note: I didn't have the unit plugged in for these shots, which is why you don't see any of the indicator lights lit up.
There are three yellow lights located over each charging bay, and a blue power indicator at the top right hand side of the unit (lights up when AC/DC power is supplied).
When you insert a battery into the charger, the three yellow lights over the bay indicate the charging status. One flashing LED on the bottom means the unit is charging, and the battery is less than 1/3 full. One solid on the bottom and one flashing LED in the middle means the unit is charging, and the battery is less than 2/3 full. Two solid and one flashing LED means the unit is charging, and the battery is more than 2/3 full. Three solid LEDs means the battery is fully charged and the unit has stopped charging.
As you can see in the pics above, all standard battery sizes fit fine. I was able to get my longest high-capacity 18650s to fit (although they were a bit snug). I was even able to get the 26650 from my 4Sevens X10 to charge fine. I can't guarantee that all 26550 cells will fit, however (i.e., a smaller positive button on the cell may not be able reach to the positive contact plate in the bay).
Here is a quick video overview of the physical build of the charger:
Video was recorded in 720p, but YouTube typically defaults to 360p. Once the video is running, you can click on the configuration settings icon and select the higher 480p to 720p options. You can also run full-screen.
To examine the performance of the charger, I have directly monitored charging current and voltage with a data-logging DMM (on separate runs).
For these tests, I have used my standard AW protected 18650 (2200mAh) and RCR (750mAh) cells, and Sanyo Eneloop AA NiMH. The cells used here have all had a good number of cycles on them, but are still in reasonable condition. To deplete the cells, I used my regular test bed of a fully-regulated JetBeam Jet-III ST, Jet-II or Jet-I Pro (all IBS models) on Max output – and wait until the cell’s protection circuit gets tripped. The cell is then immediately loaded into the charger for testing and recording (depleted resting voltage typically ~3.0-3.2V).
Let's start with something simple: 1x18650, and 1xRCR:
The i4 V2 shows a charging algorithm on 1x18650 that at least approximates the CC/CV charger pattern for Li-ions. The initial charging current (measured at 750mA) is exactly as reported for this charger.
In the 1x18650 run above, you can see the i4 kept the charge current very constant during the CC phase, and dropped down gradually during the CV phase. The CV phase doesn't appear to exactly constant, but it's not bad.
Ok, this a little different. For the 1xRCR run, the unit was not able to keep the CC phase for long, and quickly dropped into the CV phase.
UPDATE: As noted in the discussion below, the charger does not seem to have a true CV phase, but rather something that approximates it. I have not tested enough chargers to know for sure what this phase normally looks like on 1xRCR.
For both runs, the unit terminated at just under 40mA charging current. This is very respectable, and means that lower capacity Li-ions can be safely charged in the light (e.g. RCR, 14500, 10440, etc.). Of course, this specific CC/CV-like pattern also means that cells will take a bit longer than in some other chargers.
Fully charged, most of my well-used cells were ~4.16-4.18V at rest. With newer cells, I measured ~4.20-4.21V at rest. This is normal (cell capacity drops with repeated cycles), and suggests the charger is charging up to the full capacity of the cells.
The i4 does not completely terminate when the three yellow LEDs go solid. Although my DMM dropped to zero on my 10A port, when I switched over an re-ran the termination charge on my DMM’s mA/uA port, I measured a low 110 uA current. But this is low enough to be irrelevant. Note that despite what the manual says, this is not what most people understand as a "trickle charge." A true "trickle charge" usually involves a regular pulse of mA current, to maintain the fully charged state. IMO, this is not a good thing for Li-ions – most "trickle chargers" are set too high, and over the long-term, will slowly cook your batteries (i.e. it gradually over-charges the cell, as long as it sits in the charger). The constant low uA current here is negligible, and will not lead to "trickle-charger" over-charging. For all intents and purposes, the i4 is close enough to full termination.
Note: The "dips" in the graphs above have to do with how the charger operates – it actually stops charging once every two seconds to check to see if anything has been inserted into the paired charging bay. I don't have an oscilloscope to show you the exact pattern, but I can estimate from my sampling measures that it takes just under a third of a second to check. This is enough to drop the current/voltage reading in the traces above. My sampling rate is once every 30 secs, hence the why you don't see a continuous "wall of noise", but just sporadic dips (i.e. there is a ~15% chance my DMM will be taking a reading during a charging pause).
Let's see what happens if you charge two cells in paired bays (i.e. #1 & 3, or #2 & #4)
While this may look similar to the earlier 1xRCR charge cycle, please pay attention to the timescale. As you will see, it took a lot longer to charge two cells in the paired bays. The reason for this is that the charger alternates the current between the cells (i.e. charges the first bay for a little under one sec, then stops and charges the other bay for a little under one sec, etc.). Note also the charger still does its ~1/3 sec pause every ~2 secs to check the status of the paired bay.
The net effect is roughly comparable to what would happen if each bay got a continuous half-current instead of an intermittent full current (i.e., 375mA to start, instead of 750mA), assuming the same CC/CV-like pattern.
So, effectively, this means is that it may take up to twice as long to charge cells in paired channel bays (e.g., I would expect 10+ hours to charge two 18650 cells in paired bays). You could still charge two 18650 cells in ~5 hours using the independent channels (which I recommend). But if you wanted to charge 3-4 cells at once, at least some of those cells would take twice as long.
So why does the charger do this? Well, the 750mA initial charging rate is high for lower capacity cells (e.g. 10440). If you are trying to charge cells with low capacities (basically, anything AAA-sized or smaller), it is recommended by the manufacturer that you always charge two cells at a time, in the paired bays to lower the overall average current to each cell.
Again, remember that if I had charged these cells in bays #1 & #2, #2 & #3, #3 & #4, or #1 & #4, each one would have gotten the full charge cycle and looked just like my earlier 1xRCR current charging trace.
So how does NiMH look?
The charger runs at a CC cycle of just over ~700mA in my testing.
Unlike Li-ion, NiMH chargers don't work by a CC/CV method. Instead, they typically terminate when the battery reaches a particular voltage level, based on a characteristic increase in the positive slope of voltage versus time (i.e., dV/dT). As you can see in my runtime traces, there is a very pronounced uptick in voltage just before the run terminates. But I haven't tested other NiMH chargers, so I don't know if this is what to expect for dV/dT termination. Any of the NiMH experts want to chime in here?
The full charge capacity seems to be good. My Maha C9000 charger typically charges this cell to ~1950mA, and reports the discharge capacity as ~1850mA. When I discharged the i4-charged cell, I got ~1830mA discharge capacity, which is pretty comparable to what my Maha reports after its own charge/discharge cycle.
Oh, and some good news: it looks like you can charge both NiMH and Li-ions at the same time, even in paired bays. I know there were some issues reported with this on the first (recalled) version of the i4. But I've tested it in a variety of bays, and NiMH and Li-ion both charged correctly (at least based on initial charging patterns – I didn't run them until termination). The manual for the i4 V2 reports this is allowed.
The new second edition of the i4 Intellicharger from Sysmax appears to live up to the initial promise of this model. It successfully charged all manner of cells that I threw at it, with performance generally consistent with its specifications.
For Li-ions, I particularly like the use of the CC/CV-like method, with a low charging rate at the time of termination (i.e. <40mA in my tests above). This is about half that of my Pila charger, which is the gold-standard for consumer Li-ion chargers. A low termination current is important for low-capacity cells (i.e., RCR and anything smaller), which suggests you are good to charge anything here.
However, because of the relatively high initial charging current on Li-ions (750mA), you shouldn't charge anything smaller than RCR individually. Sysmax recommends you charge anything with the capacity of AAA/10440 or smaller in pairs, on the same current channel (i.e. bays #1 & #3, or #2 & #4). As this is a four-bay charger with only two independent channels, the charging current will be essentially halved when you charge two cells simultaneously in those bays. If you want to charge two cells simultaneously with the full current to each, you would need to place them in bays #1 & #2, #2 & #3, #3 & #4, or #1 & #4.
The charger suspends charging for just under 1/3 of a second every 2 seconds, to check the status of the other bay. This means that the charger is only charging a single cell ~85% of the time (or ~42% of the time, if running in paired charging bays).
The end result of all of the above means that it takes a little longer to fully charge your cells. For one 18650 2200mAh cell (or two cells in independent channels), I would plan for at least 5 hours charging time from fully depleted (my Pila takes a little over 4 hours, in comparison). As an aside, for those who complain that four 18650s would take 10+ hours on the i4, I would point out my Pila would need 8+ hours anyway (i.e., I would have to switch the two cells out after 4 hours, or buy a second Pila!).
The i4 V2 charger dropped to a negligible low uA once the status lights indicated a full-charge. Despite what the manual says, this is not a "trickle-charge" – it is in fact much better, and is practically equivalent to actual full termination.
The i4 also successfully handled any NiMH cells I tried on it. Charging current was constant at ~700mA over the course of the charging cycle. The i4 will certainly not replace my Maha C9000 workhorses with their detailed featured sets (yes, I own two of them ), but it gets the job done in a reasonable amount of time. I was (pleasantly) surprised to see that I could charge both Li-ions and NiMH simultaneously – in both paired and/or independent channels – and everything seemed to work fine.
Physically, the charger handled all my cells (including one 26650). However, they do need to grease the springs at the factory – most of mine were so stiff, I was worried about bending the prongs when first trying to insert the cells. The charging light interface is intuitive, and worked consistently in my testing.
End of the day, no real surprises here – the charger lived up to its billing. I hope you found the current/voltage analysis useful. But as always, I will leave it up to the battery and charger experts here to weigh in and provide more detail on the charger specifics.
UPDATE JANUARY 6, 2012: I have now reviewed a similar version of this charger, under the Jetbeam-specific branding - the Jetbeam i4 PRO.
i4 V2 charger supplied by Sysmax for review.